plastic welding

[toplessHO]

Yea I know its hard to strike an arc
but once you do its smooth going

Heres a short write up on repairs I made to gravel guards on a 2016 GM truck.

The Horror Fright hot air welder I have was way too hot
recorded up to 290*F tip temp @2psi.
So I got one of those nifty plug in speed regulators
and gave it a whirl.
At 1/2 way on the adjustment it lowered to 260*
1/4 way it dropped down to 215*F which seemed just right for melting without any destruction of surrounding areas.

 

[toplessHO]

more pics
heres the test piece,far left is full temp,middle is half temp and the puddle is 1/4 temp.

 

[toplessHO]

heres first repair,I use the same material cut into strips with tinsnips as my welding rod material.

 

[toplessHO]

repairs made on backside dont need to be pretty and I add extra at the corners and weak spots. Make sure to get it hot enough for all to meld together yet not hot enough to blow thru.Front side that shows has a crack showing,so use rod and a Popsicle stick to smooth it out.

 

[toplessHO]

a couple more smaller repairs and its all done
if its a part that shows you can finish off with filing .grinding ,sanding
and even final smoothing with a heat gun to make it look like theres no repair made.
Please note this is for only thermoset plastics only.Epoxies work for other types.

 

[6PTsocket]

I have a few points. Plastics that melt are thermoplastics. Plastics that do not melt but burn are thermosetting plastics. These are the candidates for epixies like JB weld. In many cases there is no scrap available for welding rod. There are a number of sources but Polyvance, formerly Urethane Supply has a long list of plastic welding rods to match what you are repairing and instructions on how to find a match. They offer another approach. They have another plastic rod called fiberflex that does not actually weld but bonds to the repair. It is sometimes actually stronger than a weld. Think hot melt glue on steroids. To make it stronger they sell stainless steel mesh that you can embed in the repair. I used fiberflex for a repair similar to yours when none of my limited selection of rods would weld. Sometimes the number inside the recycle triangle or the letters underneath will tell you what plastic you are dealing with. It looks like you did a good job.

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[toplessHO]

please dont use regular JB weld on plastics.
Lots of good epoxies designed for plastics
3M,Lord Fusor,Devcon are a few.
Ive used fiberflex and its good but for this application
what I used was the cheapest and easiest.
Plus it blends right in so doesnt look repaired.

 

[6PTsocket]

please dont use regular JB weld on plastics.
Lots of good epoxies designed for plastics
3M,Lord Fusor,Devcon are a few.
Ive used fiberflex and its good but for this application
what I used was the cheapest and easiest.
Plus it blends right in so doesnt look repaired.

It depends on the plastic. I have used JB Weld on a number of hard plastics with great success. If you don't like it please don't use it. It bonds well to ABS and phenolic (bakalite). If you are not in a rush you can always test it. I have had excess spots that I could not chip off I had to chisel and sand it off. There are many plastics and and no general rule that fits all. I work on a lot of car unrelated stuff so I deal with plastics that are not usually in cars. Not every 3M product is the best choice for every job, either.

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[Colin Len]

Interesting. I've never seen one of these "hot air" welders before. A car that I'm currently restoring (full exterior paint job) has tons of trim/moldings that use plastic clips. Many are hard not to break when removing and replacements are all discontinued (plus it'd be $2k+ just for all these bits anyway). This is tempting to look into a bit more.

So this is the tool you're using and you just added the speed regulator?
https://www.harborfreight.com/plastic-welding-kit-with-adjustable-temperature-96464.html

 

[toplessHO]

no mine has an air regulator with gauge(shown in first post)

they do make another that has its own air supply(built in fan)
and a temp setting but I find this one is lighter and easier to work with.
Now that I have the temperature control figured out this gun is the easiest to use.
you may end up improvising new clips and gluing some stuff on when a clip cant be found.Ive found AUVECO a good source for clips as they are an OEM supplier

 

[Colin Len]

Can you post a pic of the actual tool? I only saw 2 styles at HF and sounds like you're saying yours is like neither of them.

 

[toms73novass]

Older model they no longer sell......

 

[toplessHO]

thanks Tom
yea same model
neighbor has one also
so hope they both last us a lifetime since they quite selling them

 

[Outlander]

Interesting stuff. So, assuming we are not all gods of material science, how the heck do you figure out what kind of plastic our parts that need welding are? Please speak slowly, I did way better in physics than chemistry.

 

[Guster]

Start with the recycling code if it has one ie.
https://en.wikipedia.org/wiki/Resin_identification_code
http://chemistryaustralia.org.au//L.../c5dd1bc7-0a5a-4ef0-b81b-e703664b3c9c/pic.pdf

There is also a standard for marking injection moulded FRP/GRP components with that includes % fibre/filler ratio etc. http://www.bombardier.com/content/d...astomers-Standard-Doc-ID-number-000018-en.pdf

Else you can do a test - http://www.partec.qld.edu.au/files/Plastics_Identification_Flow_Chart.pdf

 

[toplessHO]

for me it helps to have alot of scrap plastic pieces
make sure its clean from paint,oil etc.
yes the recycle label will ID most

 

[kbs2244]

What I thought was interesting was how many of the you tube fixes did use any "filler rod."
Just re-melt the edges of the crack.

And the use of paper clips to bridge the crack!

 

[bdk1976]

Wish I would have seen this thread a couple of days ago- good advice regarding the temp control.

Just tried out my welder (the orange one pictured in a previous post) that I picked up at the Portland Swap Meet in April for $5 NIB. Had some damage to my mower's grass chute and succesfully(?) welded it up. Looks very ugly but it's on the bottom and not normally visible.

None of the three included plastic filler rods were appropriate for this application- ended up using zip ties as filler rod instead.

Hope to get some more practice in as I have several other -more visible - repairs to attempt in the future.


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[PugetDude]

I've had good luck using an old Weller soldering gun and strips of the parent material cut into slivers. The technique is similar to tig welding, you get a puddle started, push the filer into the puddle, move over, do it again...
I welded a crack across the bottom of a Homer bucket that froze a couple of years ago, it's still hanging in there after moving a ton of decorative rock two half-buckets at a time. The filler material came from the ribs near the top of the bucket.

I've used this technique on a neighbors plastic wheelbarrow and a couple of clips that hold the shades in my motorhome- used some had black nylon from an old pressure washer handle for filler on those.

 

[toplessHO]

most ty-raps are nylon and wont work for PP
they are too expensive for me to use,which is why I use parent material or find similar scrap.

 

[Dutch01]

My attempt on plastic welding

Done with electric soldering iron and pieces of plastic from broken appliances

 

[toplessHO]

Dutch lightly hit that spot with a hair dryer or heat gun
and those sanding marks will melt away


and any time you can use material from edges of the same piece the less chances of in compatibility

 

[Uswjnr05]

You need heat to actually fuse the material. Using a hot air welder will allow the material to burn and is why compressed nitrogen is used in actual plastic welders. Many body shops have purchased these units but have failed to make a profit from them for a variety of reasons. You can find them for sale used for under $200. Just like any welder, practice is the key to a quality repair.

 

[toplessHO]

theres a difference between when plastic becomes "plastic"(actual description of the state the material is in) and when it combusts.Controlling the heat is the key to making a hot air welder work. Havent had any problem using normal compressed air,and have never gotten it hot enough to smoke.Agree that like any other welding practice makes perfect

 

[6PTsocket]

Interesting. I've never seen one of these "hot air" welders before. A car that I'm currently restoring (full exterior paint job) has tons of trim/moldings that use plastic clips. Many are hard not to break when removing and replacements are all discontinued (plus it'd be $2k+ just for all these bits anyway). This is tempting to look into a bit more.

So this is the tool you're using and you just added the speed regulator?
https://www.harborfreight.com/plastic-welding-kit-with-adjustable-temperature-96464.html

Did you read your link? It says "with temperature adjustment". The OP has an older model that did not, so he had to add outboard control.

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[Bobhdus]

I have a Seelye Hot Air welder. They’re usually high dollar but can find good deals on eBay.


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[TerryH]

You need heat to actually fuse the material. Using a hot air welder will allow the material to burn and is why compressed nitrogen is used in actual plastic welders. Many body shops have purchased these units but have failed to make a profit from them for a variety of reasons. You can find them for sale used for under $200. Just like any welder, practice is the key to a quality repair.

Don't quite get why a shop would not make a profit on a nitrogen welder. We have them in our 4 shops and we do quite well with them. We charge a pretty good amount for tab repairs etc... but much more cost effective vs replacing the cover. The insurance companies eat it up. We have Polyvance machines. They do an incredible job at fusing cracks and forming tabs with the plier/mandrel kits.

 

[RPH]

There is a good resource for plastic welding, known as “the book”. It’s too large to load here. Get your copy here.
https://www.polyvance.com/thebook.pdf